Gas-fired appliances and systems in residential, commercial, and industrial applications typically are equipped with mechanical regulators that are well known in the art and have remained essentially unchanged for many years. A significant disadvantage of these mechanical regulators is that they cannot be easily or inexpensively interfaced with electronic feedback control. This becomes an increasingly serious obstacle to efficiency as more sophisticated sensors are developed for monitoring combustion efficiency in order to reduce fuel consumption, CO, and CO2.
The polluting gas NOx is also a by-product of burning fossil fuels and has come under increasing recent scrutiny at the State and Federal levels. A proven method of reducing NOx in natural gas combustion is so-called “oscillating combustion” wherein the amplitude of the natural gas flow is varied in time (U.S. Pat. Nos. 4,846,665 and 5,202,111). This application requires a regulating valve that can not only vary the frequency of the gas amplitude (e.g., about 5-10 Hz) but also be under electronic feedback control.
Embodiments of the invention by Lawless and Arenz (U.S. Pat. No. 5,222,713) satisfied the above requirements, but the embodiments may benefit from further development. A “central orifice” design and an “edge orifice” design for the elastomer were taught (see FIG. 3 and FIG. 12-B of the '713 patent), and a large force is needed to vary the size of such orifices. Such large forces are provided by electrostrictive, piezoelectric, and magnetostrictive actuators, but all carry small displacements. Small displacements may limit the possible variations in the orifice size to relatively small gas flow rates. Also, these types of actuators may be expensive, the electro- and piezoelectric actuators may be subject to long-term dielectric failure, and the magnetostrictive actuator may require an energizing magnet.
Embodiments of the present invention are refinements of the embodiments of the '713 patent relative to an apparatus for regulating the flow of fluids in general and of natural gas in particular. The embodiments of the present invention both simplify the embodiments of the '713 patent and economically allow the regulation of a much larger gas flow, while preserving the feature of controlling the flow rate via the motion-amplification of an elastomeric material. In addition, the feature of electronic feedback control is also utilized in the present embodiments.